Electroanalysis with Carbon Paste–Based Electrodes, Sensors, and Detectors - Electroanalysis with Carbon Paste Electrodes - page 187

I P
(nA)

Bare CPE Bi 30% -CPE Bi 85% -CPE

1000

800

600

400

200
-0.4 -0.6 -0.8 -0.5 -0.7 -0.4 -0.6 -0.8

E (V) vs. Ag/AgCl

FIGURE 8.13 From.the.inal.optimization.of.a.method.for.determination.of.4-amino-3-nitro.phenol.(4A3NP).
at.three.different.carbon.paste.electrodes..Sets.of.voltammograms.obtained.by.analyzing.the.compound.of.
interest.at.the.lowest.detectable.concentrations..Bare.CPE.made.from.Nujol.oil-based.carbon.paste;.Bi-CPE,.
carbon. pastes. with. bismuth. powder. admixed. at. 30%. and. 85%. (w/w).. Experimental conditions :. DPV,. scan.
rate:.20.mV.×.s −1 ,.pulse.height:.50.mV,.pulse.width:.80.ms;.supporting.electrolyte,.B-R.buffer.(pH.4,.with.10%.
MeOH;. dashed. line);. c (4A3NP). =. 4-10. ×. 10 −6 . (for. bare. CPE),. 2-10. ×. 10 −6 . (Bi 30% -CPE),. and. 1-10. ×. 10 −5 .
mol.×.L −1 .(Bi 85% -CPE);.full.line..(Redrawn.from.Dejmkova,.H..et.al.,.Application.of.carbon.paste.electrodes.
with.admixed.bismuth.powder.for.the.determination.of.4-amino-3-nitrophenol,.in. Sensing in Electroanalysis ,.
Vol.. 3,. Eds.. K.. Vytˇas,. K.. Kalcher,. and. I.. Švancara,. University. Press. Center,. Pardubice,. Czech. Republic,.
2008,.pp..83-89..With.kind.permission.of.the.authors.)

titrations. of. surfactants. as. well;. corresponding. procedures. were. reviewed. [159,1966].. In. voltam-
metric.procedures,.similar.ion-pairing.principles.as.in.potentiometry.can.be.utilized;.the.respective.
CPEs.modiied.with.compounds.containing.lipophilic.counter-ions.and.the.analytes—that.is,.cor-
responding.surfactants—are.accumulated.at.their.surfaces.[207,2463].
Organic.pollutants.known.under. commercial names .and/or. trademarks .are.then.listed.in.Table.
8.13,.documenting.that.these.substances.are.represented.mainly.by.various.pesticides.from.the.fami-
lies.of.carbamate.and.dithiocarbamate.derivatives,.organo-phosphates,.triazines,.or.polychloro-.and.
polynitro.benzenes..As.can.be.seen,.the.electrochemistry.with.CPEs.has.signiicantly.contributed.
to.developing.a.lot.of.new.procedures.for.these.traditionally.determined.organic.pollutants.[59,83].
In. association. with. momentarily. popularized. “green-chemistry”. approaches,. the. actual. impact.
of.some.widely.used.pesticides.on.the.environment.is.intended.to.be.studied.via. online monitoring .
and.evaluated.by.means.of.the. time-controlled biodegradability .[2180-2182]..For.such.purposes,.it.
is.necessary.to.have.a.reliable.method.capable.of.determining.these.compounds.at.suficiently.low.
concentrations,.including.their.residua.in.natural.matrices..Some.new.studies.have.shown.that.the.
combination.of.choice.could.be. electrochemical stripping analysis (ESA) .with.a.CPE.based.on.tricre-
syl.phosphate-containing.carbon.paste.(C/TCP).whose.electroactive.binder.can.effectively.interact.
with.lipophilic.molecules.of.some.pesticides.[2493]..One.of.the.initial.stages.of.such.environmental.
investigation.is.captured.in.Figure.8.14,.demonstrating.why.the.C/TCP.electrode.is.of.such.interest..
Regarding. the. already. existing. collection. of. organic. pollutants. determinable. at. CPEs. gathered. in.
Tables.8.12.and.8.13,.there.are.some.joint.characteristics.that.can.be.briely.commented.on.at.the.end.
of.this.section..First,.the.individual.methodological.procedures.employ.still.popular.ESA.techniques,.
often,.in.combination.with.effective.preconcentration.via.adsorption,.extraction,.or.ion-pairing.
Of.course,.should.they.be.successful.also.in.determination.of.residual.concentrations.and.analy-
sis.of.samples.with.complex.matrices,.the.corresponding.methods.must.offer.both. high selectivity
and sensitivity ,. which. demands. not. only. the. proper. working. electrode,. but. also. strictly. deined.
experimental.conditions,.mainly,.the.continuous.pH-control.